The present invention relates to a sorting apparatus and a method of control for the same.
More specifically, the invention refers to a sorting apparatus of the type including a plurality of carriages connected to each other and drawn along a fixed route by a chain or similar means, in which each carriage is provided with means which can receive an object and unload it in relation to prefixed collection stations positioned along the route.
These means are preferably made up of a rotating belt actioned by an autonomous motor mounted on the carriage and which picks up the necessary power supply through sliding bar supply contacts arranged along the route.
In conformity with the invention the carriages are gathered in more groups, which will be referred to hereafter as "shuttles". Each shuttle is provided with a CPU able to discern the signals on their arrival and send them to the preselected carriage, so as to activate the unloading devices after a preset time "t".
The invention provides that the carriage sends back, to the central unit controlling the system, a confirmation signal in the absence of which the control devices of the apparatus repeat the command previously sent to the carriage, varying the delay time "t" in relation to the space travelled in the meantime.
There are well known sorting apparatuses which include a plurality of carriages that move along one or more guide rails and on which there are arranged the objects to be sorted, which are then unloaded between collection devices positioned along the route.
One of these apparatuses is described for example in Italian patents No. 1,140,188 and no. 1,152,067 of the same applicant and includes a series of carriages, drawn by means of a chain or similar method, on each of which there is mounted a rotating belt actioned by its own motor which gets its energy supply, using sliding contacts, by a couple of feed bars which run in parallel to the guide rails.
All the apparatus functions are controlled by a central computer which monitors, moment by moment, the position of each carriage, due to signals generated by an encoder mounted on the wheel axis which sets the chain in motion. The commands for the activation of the motors which in turn activate the unloading belts for the transported objects are sent by the central computer to the various carriages by means of separated signal transport bars, these too arranged in parallel to the guide rails.
Hereafter, these bars which transport the signal will be indicated by the term "sectioned bars", while the term "continuous bars" or "feed bars" will indicate those bars from which the carriages pick up electric energy necessary for the supply of their motors and other devices on board.
The supply circuit of one of these well known apparatuses is given in diagram form in FIG. 1. FIG. 1A is perspective view of the belt and motor of FIG. 1.
Here, 1 indicates the carriages, each of which has on board a rotating belt 2 which acts as a transport floor for the objects 3 and which is actioned by its own motor 4.
The motors 4 by way of sliding contacts 5 pick up the necessary power supply from sectioned bars placed along the route, constituted by a plurality of conductors 6, each of a length less than the pitch of a carriage and separated from each other by insulating elements 7.
The functions of the system are managed by a central computer, for example a PLC8, which controls a series of power supplies or servo-amplifiers 9 which are earthed and each connected to a section of sectioned bar 6.
This solution, however, involves numerous inconveniences. Each amplifier must be able to transmit a current with an intensity greater than 15 Amp. This means that the connection to the supply bar must be made with cable of suitable dimensions.
When one considers that a normal system of this type often includes 200 or 300 carriages which sort towards what is often a similarly elevated number of collection stations, it is easy to understand how complex the apparatus is in constructional terms.
In addition to having to reposition a high number of earth actions, connecting each of them to the relevant part of the sectioned bar, problems then arise in relation to the control of electrical power in so far as the transmission of powers at such a high level through sliding contacts causes sparks. This cause the quick wearing out of the conductors.
To limit these inconveniences it is then necessary to very precisely control the activation of each section of bar, such that the transmission of power occurs only when the sliding contacts have passed the interruption zone between two consecutive bars.
The activation, in consequence, must be made with extreme precision with respect to the position of the machine, with restricted margins of error. This limits the performance, in so far as a reduced period of time is available for carrying out the unloading. When the collection stations are many and therefore of restricted dimensions, there are few milliseconds available (approx. 200) to give the rotating belt 2 the necessary acceleration for correct unloading of the object.
Other inconveniences of this solution derive from the fact that each time an amplifier is burnt the corresponding output is lost. This can be recovered only by stopping the system for the necessary repair work.
Finally, the amplifiers must be exaggeratedly sized in relation to real need, to avoid over-heating and ensure a correct functioning even in the case, although not frequent, where several carriages unload consecutively at the same station.
These inconveniences have been resolved only in part in apparatuses known more recently, the supply layout of one of which is illustrated in FIG. 2.
In these apparatuses the servo-amplifiers are mounted one per carriage and pick up the supply power by means of sliding contacts 10, from continuous bars 11.
The sectioned bars 6, in consequence, receive only control signals coming from the PLC8, and with this solution, thanks to the fact that the power to be transmitted is minimal, dangers due to sparks are avoided. There is in addition a greater amount of time available for accelerating the belt, which allows for more precise control of unloading functions.
On the other hand this solution involves a greater number of sliding contacts and therefore a greater complexity of connections, resulting in a cost which is significantly higher than the preceding solution.
For this reason there is felt to be in the sector a need to be able to use apparatuses of the above-described type, but which have limited production cost, are easy to maintain, and which allow the elimination or at least drastic reduction of the number of harnesses, thereby possibly avoiding the need to make use of sectioned bars.